The present invention relates in general to an array of resistive switching devices (RSDs). More specifically, the present invention relates to fabrication methods and resulting structures for forming a vertical array of RSDs having restricted filament regions and tunable top electrode volume.
Resistive random access memory (ReRAM) is a nano-scale non-volatile memory (NVM). ReRAM provides simple storage cell components, high density, low power, large endurance, fast write/read/erase speeds, and excellent scalability. A typical ReRAM storage cell is two-terminal device formed as a metal-insulator-metal (MIM) structure. The insulator material can be a binary metal oxide, which makes the MIM storage cell compatible with silicon-based CMOS (complementary metal oxide semiconductor) fabrication process. When a sufficient electrical signal is applied across the metal electrodes of a MIM, the resistance of the insulator can be switched from one resistance state to another. The insulator retains its current resistance state until an appropriate electrical signal is applied across the metal electrodes to change it.
ReRAM, along with the logic circuitry used to address/read/write individual ReRAM cells, can be implemented in an array (e.g., crossbar arrays), which is compatible with a variety of electronic circuits and devices, including neuromorphic architectures. Multiple pre-neurons and post-neurons can be connected through the array of ReRAMs, which naturally expresses a fully-connected neural network. The density of ReRAM can be increased by configuring the array as a three-dimensional (3D) vertical stack of addressable ReRAM cells as practiced in Flash NAND technologies.